1. Field of the Invention
The present application relates to a composition and methods to enhance nerve regeneration utilizing neural stem cells and IL12p40.
2. Description of the Related Art
Severed peripheral nerve injury causes a reduction in motor and sensory neuron activities, and degeneration of nerve fibers and the surrounding tissues. The regeneration of injured peripheral nerve is a multiplex process, with Wallerian degeneration (WD) being the most elementary reaction and Schwann cells playing an important role (Ren Z. et al., Reviews in the Neurosciences 2012, 23:135-143). WD creates a microenvironment for regeneration of surviving neurons and benefits functional recovery (Navarro X. et al., Progress in Neurobiology 2007, 82:163-201.). The control of WD involves the existence of Schwann cells, the secretion of neurotrophic factors, and special extracellular matrix that acts as a scaffold for neural cells (Gaudet A. D. et al., Journal of Neuroinflammation 2011, 8:110; Kehoe S. et al., Injury 2012, 43:553-572.).
Nerve conduits provide mechanical support and direct axonal sprouting between the injured nerve stumps. Conduits have been shown to retain neurotrophic factors secreted from or recruited by the damaged cells (Kehoe S. et al, Injury 2012, 43:553-572.) and prevent ingrowth of fibrous tissue at the injury site. Recent studies reveal that implantation of neural stem cells (NSCs) in conduits promote regeneration of injured peripheral nerves (Zhang H. et al., Journal of Translational Medicine 2008, 6:67; Shi Y. et al., Acta Oto-Laryngologica 2009, 129: 906-914.).
The promotion of nerve regeneration may depend on the ability of implanted NSCs to differentiate into Schwann cells, to secrete neurotrophic factors per se, or create a microenvironment to enrich neurotrophic factors from milieu, and to assist in myelination (Ren Z. et al., Reviews in the Neurosciences 2012, 23:135.443). However, the nature of cytokines or growth factors that are involved in this process is not clear. The molecular mechanism for the Schwann cell differentiation of the implanted NSCs into newly regenerated axons is also not well established.
In this study, it is an aim to identify factors that are involved in NSCs-mediated nerve regeneration and functional recovery. Using a protein antibody array, we searched for protein level differences in a mouse sciatic nerve injury model using conduits with or without NSCs. The levels of IL12p80 (the bioactive homodimer form of IL12p40) (Heinzel F. P. et al., Journal of Immunology 1997, 158:4381-4388) in these conduits were nearly two-fold higher than those in conduits without NSCs. Implantation of NSCs with nerve conduit and IL12p80 improved motor function in a sciatic nerve injury mouse model.
Administration of IL12p80 further enhanced nerve regeneration as evidenced by the increased diameter in the regenerated nerve, up to 4.5-fold thicker than the Conduit only group at the medial section of the regenerated nerve and improved nerve conduction. This is showed that IL12p80 induced the neuroglia differentiation of mouse NSCs in vitro through phosphorylation of signal transducer and activator of transcription 3 (Stat3). The neuroglia comprises astroglia, oligodendrocytes, and Schwann cells as reported by Kettenmann and Verkhratsky (Kettenmann H, Verkhratsky A, Fortschritte der Neurologie-Psychiatrie 2011, 79:588-597.).